NO823667L - PROCEDURE FOR PREPARING PHOTO SULPHONATES OF ALKANOLAMINES - Google Patents

Description

The present invention relates to a method for the continuous production of photo-sulfonates of alkanol-amine from a starting product (1) which consists of fatty acid, methyl esters or petroleum paraffins comprising the following steps: a) the starting product (1) is subjected to photo-sulfonation in an anhydrous environment with a mixture (3) of sulphur-sulfuric anhydride and oxygen under ultraviolet irradiation b) the product (4) from step a) is degassed for its in- hold of sulphur-acid^ranhydride and the peculiarity of the method according to the invention is that it comprises the following additional steps: c) to the degassed product (8) obtained at the output of step b) a quantity of airkanolamine (10) is added

above that which is strictly necessary for the neutralization of the contained photo-sulfonic acids, so that the thereby obtained base is deposited in two phases, a light phase of the aforementioned raffinate (11) and a heavy phase of the aforementioned extract (12)

d) the aforementioned raffinate (11) containing the unsulfonated starting product (1) (recycled to step a)\

and

e) • the aforementioned extract (12) containing the alkanolamine photo-sulphonates is isolated.

These and other steps in the invention appear from the patent claims.

By fatty esters are meant saturated methyl esters of natural origin, i.e. obtained from vegetable oils such as palm oil, soya oil or rapeseed oil or from animal fats such as e.g. lard. The fatty esters have long straight carbon chains with from 12 2 (esters of lauric acid)

to 18 (esters of stearic acid) carbon atoms. Petroleum paraffins are understood to mean alkanes with an unbranched straight chain where the chain comprises 12 to 18 carbon atoms, as well as mixtures thereof.

Photo-sulfonation of paraffins is well known and is the subject of numerous patents. Photo-sulfonation of fatty esters is specifically described in French patent application 80-00521. The present invention does not directly relate to the photo-sulfonation reaction itself, but to the steps of extraction and neutralization that follow the photo-sulfonation step.

When fatty esters or petroleum paraffins are subjected to sulphonation using a mixture of sulphur-sulfuric anhydride and oxygen under irradiation, it is found that the sulphonation does not go to completion as only part of the ester or paraffin is photo-sulphonated. In order to make the method of photosulfonation industrially profitable, it has proved necessary to recycle the unreacted ester or paraffin to the photo-sulfonation stage, and for this it has been necessary to find an extraction agent for the sulfonated compound.

In the case of photo-sulphonation of paraffins, water or methanol is used, or a mixture in any quantity ratio between water and methanol. (French patent document 1,547,452). In the case of photo-sulfonation of fatty esters, the problem is complicated by the fact that methanol is miscible with fatty esters and that the water hydrolyzes it. You can then use neither one nor the other in isolation and the French patent document 80-00521 defines the correct quantity ratios in a weakly aqueous methanol mixture by which you can carry out the extraction of sulphonated esters, i.e. that you can separate the unsulphonated esters without to hydrolyze them.

In one case or the other, the photo-sulfonated products are extracted in the state of sulfonic acids and these acids are then neutralized with sodium hydroxide, usually to give sodium sulfonates which are used in commercial detergents.

One of the purposes of the present invention is also

to provide a method which simultaneously allows extraction of unsulfonated products and neutralization of the sulfonated products.

Another object of the invention is a method of this type which can be carried out continuously.

These objects are surprisingly achieved by the present invention.

When carrying out step c), a quantity of alkanolamine sufficient to raise the pH to at least 8 is preferably added.

Step c) is preferably carried out at a temperature between 40 and 60°C.

The alkanolamine is preferably selected from the group consisting of monoethanolamine, diethanolamine, triethanolamine, monoisopropylamine, diisopropylamine, triisopropylamine and their mixtures.

In a preferred embodiment of the invention, the fatty acid methyl esters which constitute the starting product are obtained by methylation of animal or vegetable oils and fats of natural origin, followed by an extraction or a hydrogenation of unsaturated compounds.

In another preferred embodiment, the petroleum paraffins which make up the starting product have straight carbon chains containing 12 to 18 carbon atoms, or mixtures thereof are used.

The following description illustrates the invention while also referring to the attached figure?

From the aforementioned figure, it appears that the methyl fatty acid esters or the petroleum paraffins which make up the starting product (1) are introduced into a photo-sulfonation reactor (2). The sulphonating mixture (3), which consists of sulfuric anhydride and oxygen, is introduced into the reactor (2) and dispersed in the reaction mixture by means of suitable means for gas/liquid injection. This reactor (2) is subjected to ultraviolet irradiation using known devices.

From the reactor (2), the sulfonation product (4) obtained at the end of step a) with the above-mentioned photo-sulfonation is continuously withdrawn and the product is degassed in a degassing device (5) in which a flow (6) of air, nitrogen or oxygen is conducted (step b) and this removes the sulfuric acid anhydride (7) which is recycled to the photo-sulfonation reactor (1).

The degassed sulfonation product (8) is introduced into a decanting-mixing device (9) into which an alkanolamine (10) is simultaneously introduced. rDéfcte alkanolamine (10) is selected from the group consisting of monoethanolamine, diethanolamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, or their mixtures.

These products are actually very polar at the same time and they are therefore not miscible with the fatty esters or the petroleum paraffins, while on the other hand they are sufficiently basic to neutralize the strong acids formed by the photo-sulfonic acids.

In the case of the fatty esters, the alkanolamines have the great advantage that they do not saponify at temperatures close to ordinary temperatures in contrast to e.g. a solution of sodium hydroxide which is a much stronger base.

For the extraction and neutralization of the photo-sulfonic acids, more alkanolamine is added to the crude mixture from the photo-sulfonation than is strictly necessary for neutralization of the formed acids (the exact neutralization point can be easily determined by measuring the corresponding pH value which is approximately 6). A pH value of at least 8 is then achieved. It has also been observed that it is only necessary to raise the temperature to 50°C to achieve a good extraction, and this represents a certain advantage.

At the output of this step c) one obtains, firstly, a light raffinate phase (11) containing the unsulphonated fatty acid methyl esters or petroleum paraffins and which is recycled to the photo-sulphonation reactor (1) and, on the other hand, a heavier extract phase (12) containing the sulfonic acids as well as alkanolamino and unsulfonated fatty material.

This extract (12) is then introduced into a vacuum evaporation device to remove unsulfonated fatty material and alkanolamine. In the case of fatty acid methyl esters, the unsulfonated components can also be amidated with the aid of residual alkanolamine using techniques well known to those skilled in the art, avoiding the evaporation step in this case.

The following examples illustrate the invention.

EXAMPLE I

100 g of methyl stearate are introduced into the reactor (2) where a photo-sulfonation is carried out under normal conditions, i.e. under injection. of a stream (3) of gaseous sulfur-acidic anhydride and oxygen under simultaneous irradiation by means of a mercury lamp with ultraviolet radiation. A partially sulphonated product (8) weighing 106 g is obtained in about 1 hour. To this product (8) maintained at 50°C is added

16 g of monoethanolamine (10). After stirring, the mixture settles quickly and separates into two parts, one of which is the raffinate (11) weighing 58 g and the other the extract (12) weighing 64 g. The composition of the raffinate (11) and the extract ( 12) is given in the following table in % by weight.

m SEA = ethanolamine monosulfonate

d SEA = ethanolamine disulfonate

SO4.EA = ethanolamine sulfate

MEA = monoethanolamine

FE = fatty ester, i.e. methyl stearate in this example.

The analyzes were carried out using techniques well known to those skilled in the art. The monosulfonic acid, the active ingredient, was determined by the Epton method. The dissulfonic acid was determined by means of titration in an anhydrous environment which allows, on the one hand, the determination of the second dissociation acidity in the sulfuric acid and, on the other hand, the strong acids formed by the first dissociation acidity for sulfuric acid and the sulphonic acid acidity. The fatty esters (methyl stearate)

was determined by extraction with petolether. Finally, residual free monoethanolamine was determined by titration with hydrochloric acid.

It is established that the raffinate (11) practically only contains fatty esters and can therefore be recycled directly to the photo-sulfonation step. The extract (12) contains all the synthetic sulphonic acids, in the form of salts of monoethanolamine. It is further observed that when the photo-sulfonation is carried out in an anhydrous state, the amount of sulfuric acid formed is only a few percent and consequently does not need to be removed from the product. For use as an active ingredient in detergents, the extract (12) only needs to be purified from monoethanolamine and residual unsulfonated fatty esters that it contains, and this is easily done by evaporation under a more or less powerful vacuum.

EXAMPLE II

In the photo-sulfonation reactor (2) 100 g of

a paraffin fraction (1) containing 90% n-alkanes with 14 - 17 carbon atoms, a maximum of 5% n-alkanes with 13 - 13 carbon atoms and a maximum of 5% n-alkanes with 18 or more carbon atoms. The average number of carbon atoms is 15. This mixture is photo-sulfonated in the anhydrous state under the usual conditions, i.e. by passing it through a stream (3) of gaseous sulfur dioxide and oxygen and at the same time being irradiated by means of a mercury lamp with ultraviolet radiation. A partially sulphonated product (8) weighing 108 g is obtained in about 1 hour. 12 g of monoethanolamine (10) is added to the product maintained at 50°C. After stirring, the mixture is quickly settled and separated into two parts, namely a raffinate part (11) weighing 71 g and secondly the extract (12) weighing 49 g. The composition of the raffinate (11) and the extract (12) is given in the following table II in weight%.

As in the case of the fatty esters, it is seen that the raffinate (11) which is recycled contains only unsulfonated paraffins and that the extract (12) containing the desired sulfonates can be easily purified by evaporation of the monoethanolamine and unsulfonated fatty materials.

The products obtained in accordance with the invention are particularly interesting as surface-active agents, as they have as good detergent properties as sulfonates obtained by sulfonation using sulfuric anhydride and are more easily soluble in water at normal temperature due to the distribution of the sulfonic acid radical along the chain , so that it is not necessary to add hydrotropic agents to detergents where these form the active ingredient.

Claims (6)

1. Process for the continuous production of alkanolamine photo-sulphonates from a starting product (1) which consists of fatty acid methyl esters or petroleum paraffins comprising the following steps: a) the starting product (1) is subjected to a photo-sulfonation in an anhydrous environment by means of a mixture (3) of sulfur-acidic anhydride and oxygen under ultraviolet radiation; ; and b) the product (4) from step a) is subjected to degassing to remove the content of sulphur-acidic anhydride, characterized in that it comprises the following additional steps c) to the degassed product (8) obtained at the end of step b) a quantity of alkanolamine (10) greater than that which is strictly necessary for neutralization of the contained photo-sulfonic acids is added, in that the resulting mixture is allowed to settle into two phases, namely a light raffinate phase (11) and a heavy extract phase (12) d) the aforementioned raffinate (11) containing unsulfonated starting product (1) is recycled to step a) and e) the aforementioned extract (12) containing the desired alkanolamine photo-sulfonates is isolated. 2. Method as stated in claim 1, characterized in that to step c) an amount of alkanolamine (10) sufficient to raise the pH in the mixture to at least (8) is added. 3. Method as stated in claim 1 or 2, characterized in that step c) is carried out at a temperature between 40 and 60°C. 4. Method as set forth in claims 1-3, characterized in that the ethanolamine (10) used is selected from the group consisting of monoethanolamine, diethanolamine, triethanolamine, monoisopropylamine, diisopropylamine and triisopropylamine and their mixtures. 5. Method as stated in claims 1-4, characterized in that the methylated fatty acid esters used as starting material are obtained by methylation of natural oils and fats of animal or vegetable origin followed by an extraction or hydrogenation of unsaturated compounds. 6. Method as stated in claims 1-4, characterized in that the petroleum paraffins used as starting material have straight carbon chains containing 12 to 18 carbon atoms, or mixtures thereof.